Parallel assembly of discrete components onto a substrate

ABSTRACT

A method includes transferring multiple discrete components from a first substrate to a second substrate, including illuminating multiple regions on a top surface of a dynamic release layer, the dynamic release layer adhering the multiple discrete components to the first substrate, each of the irradiated regions being aligned with a corresponding one of the discrete components. The illuminating induces a plastic deformation in each of the irradiated regions of the dynamic release layer. The plastic deformation causes at least some of the discrete components to be concurrently released from the first substrate.

CLAIM OF PRIORITY

This application is a continuation of U.S. application Ser. No.16/621,432, filed on Dec. 11, 2019, which is a 371 application ofPCT/US2018/029347, filed on Apr. 25, 2018, and claims priority to U.S.Patent Application Ser. No. 62/518,270, filed on Jun. 12, 2017, thecontents of which are incorporated here by reference in their entirety.

BACKGROUND

This description relates generally to assembling discrete componentsonto a substrate.

SUMMARY

In an aspect, a method includes transferring multiple discretecomponents from a first substrate to a second substrate, includingconcurrently irradiating multiple regions on a top surface of a dynamicrelease layer, the dynamic release layer adhering the multiple discretecomponents to the first substrate, each of the irradiated regions beingaligned with a corresponding one of the discrete components. Theirradiating induces an ablation of at least a portion of the dynamicrelease layer in each of the irradiated regions. The ablation causes atleast some of the discrete components to be concurrently released fromthe first substrate.

Embodiments can include one or more of the following features.

Irradiating the multiple regions includes irradiating the multipleregions with laser energy. The method includes separating the laserenergy into multiple beamlets, and irradiating each of the multipleregions with one of the beamlets of laser energy. The method includesseparating the laser energy with a diffractive optical element. Theirradiating induces ablation of a partial thickness of the dynamicrelease layer in each of the irradiated regions. The ablation of thepartial thickness of the dynamic release layer induces a deformation ofa remaining thickness of the dynamic release layer in each of theirradiated regions. The deformation includes a blister in each of theirradiated regions of the dynamic release layer, the blisters eachexerting a force on the corresponding discrete component. The forceexerted by the blisters causes the discrete components to be releasedfrom the first substrate. The ablation of the partial thickness inducesa plastic deformation in each of the irradiated regions. The ablation ofthe partial thickness induces an elastic deformation in each of theirradiated regions. The irradiating induces ablation of an entirethickness of the dynamic release layer in each of the irradiatedregions. The method includes reducing an adhesion of the dynamic releaselayer prior to irradiating the multiple regions. Reducing an adhesion ofthe dynamic release layer includes exposing the dynamic release layer toa stimulus. Exposing the dynamic release layer to a stimulus includesexposing the dynamic release layer to one or more of heat andultraviolet light. Transferring the multiple discrete componentsincludes transferring a first set of one or more discrete components toa first target substrate, the discrete components in the first setsharing a first common characteristic; and transferring a second set ofone or more discrete components to a second target substrate, thediscrete components in the second set sharing a second commoncharacteristic. The discrete components include light emitting diodes(LEDs), and in which the characteristic includes one or more of anoptical characteristic and an electrical characteristic. Transferringthe multiple discrete components to the second substrate includestransferring fewer than all of the discrete components from the firstsubstrate to the second substrate. The method includes, beforetransferring the multiple discrete components, transferring each of oneor more of the discrete components individually from the first substrateto a destination. Transferring each of one or more of the discretecomponents individually includes transferring the discrete componentsthat do not satisfy a quality criterion. The method includes, aftertransferring the multiple discrete components to the second substrate,transferring each of one or more discrete components that remain on thefirst substrate individually to the second substrate. The methodincludes, after transferring the multiple discrete components to thesecond substrate, transferring each of one or more discrete componentsfrom a third substrate individually to the second substrate. Themultiple discrete components form an array of discrete components on thesecond substrate, and in which transferring each of one or more discretecomponents that remain on the first substrate includes transferring adiscrete component to an empty position in the array on the secondsubstrate. Irradiating multiple regions includes scanning theirradiation to multiple subsets of discrete components. The multiplediscrete components in each subset are released concurrently, and themultiple subsets are released successively. Irradiating multiple regionsincludes irradiating each region with an irradiation pattern. The methodincludes separating laser energy into the irradiation pattern. Themethod includes separating the laser energy into the irradiation patternwith a first diffractive optical element. The method includes separatingthe irradiation pattern into multiple beamlets of laser energy, eachbeamlet having the irradiation pattern. The method includes separatingthe irradiation pattern into multiple beamlets with a second diffractiveoptical element. The method includes scanning the multiple beamlets oflaser energy, each having the irradiation pattern, to multiple subsetsof discrete components. The method includes separating laser energy intomultiple beamlets of laser energy, each beamlet having the irradiationpattern, with a single diffractive optical element. The irradiationpattern includes multiple beamlets of laser energy, each beamletcorresponding to a particular location on a given discrete component.The irradiation pattern includes four beamlets of laser energy, eachbeamlet corresponding to a corner of a given discrete component.Transferring the multiple discrete components from the first substrateto the second substrate includes transferring the multiple discretecomponents to the second substrate in a face-down orientation. Themultiple discrete components include light emitting diodes (LEDs).

In an aspect, an apparatus includes a substrate assembly, including asubstrate, a dynamic release layer disposed on a surface of thesubstrate, and multiple discrete components adhered to the substrate bythe dynamic release layer; and an optical system including at least oneoptical element configured to separate a laser beam from a source oflaser energy into multiple beamlets, each beamlet configured toilluminate a corresponding region on a top surface of the dynamicrelease layer.

Embodiments can include one or more of the following features.

The at least one optical element is configured to separate the laserbeam from the source into the multiple beamlets, each beamlet having anirradiation pattern. The irradiation pattern includes multiple beamletsof laser energy, each beamlet of the irradiation pattern configured toilluminate a particular location on a given discrete component. Theoptical system includes a first optical element configured to separatethe laser beam from the source into the irradiation pattern; and asecond optical element configured to separate the irradiation patterninto the multiple beamlets, each beamlet having the irradiation pattern.The first and second optical elements each include a diffractive opticalelement. The optical system includes a first optical element configuredto separate the laser beam from the source into the multiple beamlets;and a second optical element configured to separate each of the multiplebeamlets into the irradiation pattern. The apparatus includes a scanningmechanism configured to scan the multiple beamlets of laser energy tomultiple regions of the dynamic release layer, each region of thedynamic release layer adhering a subset of the multiple discretecomponents to the substrate. The optical system has (i) a firstconfiguration in which the optical element is in the path of the laserbeam between the source of laser energy and the dynamic release layerand (ii) a second configuration in which the optical element is not inthe path of the laser beam between the source of laser energy and thedynamic release layer. When the optical system is in the firstconfiguration, the optical element separates the laser beam into themultiple beamlets. When the optical system is in the secondconfiguration, the laser beam is incident on the top surface of thedynamic release layer at a location corresponding to a location of oneof the discrete components. The apparatus includes a controllerconfigured to control the alignment of the laser beam with the locationof the one of the discrete components. The controller is configured tocontrol the alignment of the laser beam based on information indicativeof one or more of a characteristic and a quality of each of one or moreof the discrete components. The optical system includes a first opticalelement configured to separate the laser beam into a first number ofbeamlets; a second optical element configured to separate the laser beaminto a second number of beamlets; and a switching mechanism configuredto position the first optical element or the second optical element inthe path of the laser beam. The apparatus includes the source of laserenergy. The source of laser energy includes a laser. The irradiation ofthe regions of the dynamic release layer causes release of the discretecomponents aligned with the irradiated regions. One or more of awavelength and fluence of each beamlet of the laser energy is sufficientto induce an ablation of at least a partial thickness of the dynamicrelease layer in each of the irradiated regions. The wavelength orfluence of each beamlet is sufficient to induce an ablation of a partialthickness of the dynamic release layer in each of the irradiatedregions, the ablation of the partial thickness inducing a deformation ineach of the irradiated regions. The wavelength or fluence of eachbeamlet is sufficient to induce an ablation of an entire thickness ofthe dynamic release layer in each of the irradiated regions. An adhesionof the dynamic release layer is responsive to a stimulus. The adhesionof the dynamic release layer is responsive to one or more of heat andultraviolet light. The discrete components include LEDs.

In an aspect, an apparatus includes a source of laser energy; asubstrate holder configured to receive a substrate; an optical systemincluding a first optical element configured to separate a laser beamfrom the source of laser energy into multiple beamlets, in which theoptical system has a first configuration in which the first opticalelement is disposed in the path of laser energy between the source oflaser energy and the substrate holder and at least one secondconfiguration, the at least one second configuration being one or moreof (i) a configuration in which a second optical element is disposed inthe path of the laser energy and (ii) a configuration in which neitherthe first optical element nor the second optical element is in the pathof laser energy; and a controller configured to control theconfiguration of the optical system.

Embodiments can include one or more of the following features.

The apparatus includes a scanning device configured to scan the laserbeam or beamlets output from the optical system relative to thesubstrate holder. The controller is configured to move the first opticalelement into and out of the path of the laser energy. The apparatusincludes a stimulus application device configured to output a stimulusincluding one or more of ultraviolet light and heat. When a substrate ispresent in the substrate holder, the stimulus application device ispositioned to apply the stimulus to the substrate.

In an aspect, an apparatus includes a source of laser energy; a firstsubstrate holder configured to receive at least one first substrate; anoptical system including a first optical element configured to separatea laser beam from the source of laser energy into multiple beamlets, inwhich the optical system has a first configuration in which the firstoptical element is disposed in the path of laser energy between thesource of laser energy and the first substrate holder and at least onesecond configuration, the at least one second configuration being one ormore of (i) a configuration in which a second optical element isdisposed in the path of the laser energy and (ii) a configuration inwhich neither the first optical element nor the second optical elementis in the path of laser energy; a first controller configured to controlthe configuration of the optical system; a second substrate holderconfigured to hold at least one second substrate, at least a portion ofthe second substrate holder being disposed below the first substrateholder; and a second controller configured to control the positioning ofthe second substrate holder relative to the first substrate holder. Theapparatus includes a scanning device configured to scan the laser beamor beamlets output from the optical system relative to the substrateholder. The apparatus includes a stimulus application device configuredto output a stimulus including one or more of ultraviolet light andheat. The apparatus includes a control system, the control systemincluding the first controller and the second controller. The secondsubstrate holder is configured to hold multiple second substrates. Theapparatus includes a substrate rack configured to hold multiple secondsubstrates; and a transfer mechanism controllable by the secondcontroller to transfer one of the multiple second substrates from thesubstrate rack to the second substrate holder. The first substrateholder is configured to hold multiple first substrates. The apparatusincludes a substrate rack configured to hold multiple first substrates;and a transfer mechanism controllable by a third controller to transferone of the multiple first substrates from the substrate rack to thefirst substrate holder.

In an aspect, a method includes transferring multiple discretecomponents from a substrate, the discrete components being adhered tothe substrate by a dynamic release layer, the transferring includingindividually transferring each of one or more first discrete componentsfrom the substrate to a first destination using a first laser-assistedtransfer process, the first discrete components not satisfying a qualitycriterion; and transferring multiple second discrete components from thesubstrate to a second destination using a second laser-assisted transferprocess, the second discrete components satisfying the qualitycriterion.

Embodiments can include one or more of the following features.

Transferring multiple second discrete components includes transferringfewer than all of the second discrete components such that one or moresecond discrete components remain adhered to the substrate. The methodincludes individually transferring each of one or more of the seconddiscrete components that remain adhered to the substrate to the seconddestination. The multiple second discrete components form an array ofdiscrete components at the second destination, and in which individuallytransferring each of one or more of the second discrete components thatremain includes transferring each of the remaining second discretecomponents to an empty position in the array. The second laser-assistedtransfer process includes irradiating multiple regions on a top surfaceof the dynamic release layer, each of the irradiated regions beingaligned with a corresponding one of the second discrete components, inwhich the irradiation causes the second discrete components to beconcurrently released from the substrate. The first laser-assistedtransfer process includes, for each of the first discrete componentsirradiating a region on a top surface of the dynamic release layer, theregion being aligned with the first discrete component, in which theirradiation causes the first discrete component to be released from thesubstrate. The method includes reducing an adhesion of the dynamicrelease layer prior to transferring the one or more first discretecomponents. Reducing an adhesion of the dynamic release layer includesexposing the dynamic release layer to one or more of heat andultraviolet light. The second destination includes a target substrate,and in which transferring the multiple second discrete components to thesecond destination includes transferring the second discrete componentsset onto an attachment element disposed on a top surface of the targetsubstrate. The method includes curing the attachment element to bond thetransferred second discrete components to the target substrate. Curingthe attachment element includes exposing the attachment element to oneor more of heat, ultraviolet light, and mechanical pressure. The methodincludes applying the attachment element to the target substrate. Thesecond destination includes a target substrate, and including bondingthe transferred second discrete components to the target substrate. Thesecond destination includes a target substrate having circuitcomponents, and in which the method includes interconnecting circuitcomponents of the transferred second discrete components to the circuitcomponents of the target substrate. The method includes transferring thediscrete components from a donor substrate to the substrate.Transferring the discrete components from the donor substrate to thesubstrate includes contacting the dynamic release layer on the substrateto the discrete components on the donor substrate. The method includessingulating the discrete components on the donor substrate. The donorsubstrate includes a dicing tape. The donor substrate includes a wafer.The method includes applying the dynamic release layer to the substrate.

In an aspect, a method includes transferring discrete components from acarrier substrate to each of multiple target substrates, the discretecomponents being adhered to the carrier substrate by a dynamic releaselayer, the transferring including using a laser-assisted transferprocess, transferring a first set of the discrete components to a firsttarget substrate using a laser-assisted transfer process, the discretecomponents in the first set sharing a first characteristic; and usingthe laser-assisted transfer process, transferring a second set of thediscrete components to a second target substrate, the discretecomponents in the second set sharing a second characteristic differentfrom the first characteristic.

Embodiments can include one or more of the following features.

The method includes transferring the discrete components from multiplecarrier substrates to the multiple target substrates. The methodincludes transferring the discrete components consecutively from each ofthe multiple carrier substrates. The transferring includes transferringdiscrete components from a first carrier substrate to one or more of thetarget substrates in a transfer system; removing the first carriersubstrate from a transfer position in the transfer system; placing asecond carrier substrate in the transfer position; and transferringdiscrete components from the second carrier substrate to one or more ofthe target substrates. The transferring includes transferring the firstset of discrete components to the first target substrate in a transfersystem; removing the first target substrate from a transfer position inthe transfer system; and placing the second target substrate in thetransfer position for transfer of the second set of discrete components.The discrete components include LEDs, and in which the first and secondcharacteristics include one or more of an optical characteristic and anelectrical characteristic. Transferring each set of the discretecomponents to the corresponding target substrate includes transferringeach of the discrete components in the set individually to the targetsubstrate. Transferring each set of discrete components to thecorresponding target substrate includes concurrently transferring someor all of the discrete components in the set to the target substrate.Transferring a set of discrete components to the corresponding targetsubstrate includes transferring the discrete components in the set ontoa layer of die catching material disposed on a top surface of the targetsubstrate. The method includes applying the die receiving material toeach target substrate. The method includes reducing an adhesion of thedynamic release layer. Reducing an adhesion of the dynamic release layerincludes exposing the dynamic release layer to one or more of heat andultraviolet light. The method includes transferring the discretecomponents from a donor substrate to the carrier substrate. Transferringthe discrete components from the donor substrate to the carriersubstrate includes contacting the dynamic release layer on the carriersubstrate to the discrete components on the donor substrate. The donorsubstrate includes a dicing tape. The donor substrate includes a wafer.The method includes applying the dynamic release layer to the carriersubstrate.

In an aspect, an apparatus includes a substrate, multiple pockets beingformed in a top surface of the substrate; spectrum shifting materialdisposed in each of the multiple pockets, the spectrum shifting materialconfigured to emit light at one or more emission wavelengths responsiveto absorbing light at an excitation wavelength; and a LED disposed ineach of the multiple pockets, each LED configured to emit light at theexcitation wavelength, each LED oriented such that light emitted fromthe micro-LED illuminates the spectrum shifting material disposed in thecorresponding pocket.

Embodiments can include one or more of the following features.

The spectrum shifting material includes a first spectrum shiftingmaterial configured to emit light at a first emission wavelength; and asecond spectrum shifting material configured to emit light at a secondemission wavelength. The first spectrum shifting material is disposed ina first subset of the multiple pockets and the second spectrum shiftingmaterial is disposed in a second subset of the multiple pockets. Thepockets are arranged in a two-dimensional array, and in which the firstspectrum shifting material is disposed in pockets in first rows of thearray and the second spectrum shifting material is disposed in pocketsin second rows of the array. The spectrum shifting material includes athird spectrum shifting material configured to emit light at a thirdemission wavelength, and in which the first emission wavelengthcorresponds to red light, the second emission wavelength corresponds togreen light, and the third emission wavelength corresponds to bluelight. The LEDs are oriented such that a light-emitting face of each LEDfaces away from the top surface of the substrate. Each LED includescontacts formed on a second face of the LED, the second face oppositethe light-emitting face. The apparatus includes electrical connectionlines in electrical contact with the contacts of the LEDs. The substrateis transparent to light at the one or more emission wavelengths. Thesubstrate absorbs light at the excitation wavelength. The apparatusincludes a planarization layer formed on the top surface of thesubstrate. The planarization layer is transparent to the one or moreemission wavelengths. The spectrum shifting material includes one ormore of phosphors, quantum dots, and organic dye. The apparatus includesa display device. Each pocket, the spectrum shifting material disposedtherein, and the corresponding LED corresponds to a sub-pixel of thedisplay device. The apparatus includes a solid state lighting device.

In an aspect, a method includes disposing spectrum shifting material ineach of multiple pockets formed in a top surface of a substrate, thespectrum shifting material configured to emit light at one or moreemission wavelengths responsive to absorbing light at an excitationwavelength; and assembling a LED into each of the multiple pockets, eachLED configured to emit light at the excitation wavelength, each LEDoriented such that light emitted from the LED illuminates the spectrumshifting material disposed in the corresponding pocket.

Embodiments can include one or more of the following features.

The method includes forming the multiple pockets in the top surface ofthe substrate. The method includes forming the multiple pockets by oneor more of embossing and lithography. Disposing the spectrum shiftingmaterial includes disposing a first spectrum shifting material in afirst subset of the multiple pockets, the first spectrum shiftingmaterial configured to emit light at a first emission wavelength; anddisposing a second spectrum shifting material in a second subset of themultiple pockets, the second spectrum shifting material configured toemit light at a second emission wavelength. Assembling a LED into eachof the multiple pockets includes assembling the LEDs such that alight-emitting face of each micro-LED faces away from the top surface ofthe substrate. Assembling a-LED into each of the multiple pocketsincludes concurrently transferring multiple LEDs into correspondingpockets. Concurrently transferring multiple LEDs includes transferringthe multiple LEDs by a massively parallel laser-assisted transferprocess. The method includes forming an electrical connection to eachLED. The method includes forming an electrical connection to a contacton a second face of each LED, the second face opposite a light-emittingface of each LED. The method includes forming a planarization layer onthe top surface of the substrate.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams of a laser-assisted transfer process.

FIGS. 2A-2C are diagrams of a laser-assisted transfer process.

FIG. 3 is a diagram of a laser-assisted transfer process.

FIG. 4 is a diagram of a laser-assisted transfer process.

FIGS. 5A-5C are diagrams of a good-die-only transfer process.

FIGS. 6A-6C are diagrams of a good-die-only transfer process.

FIG. 7 is a diagram of an apparatus.

FIG. 8 is a diagram of a component sorting process.

FIG. 9 is a flow chart.

FIG. 10 is a diagram of a laser-assisted transfer process.

FIGS. 11A and 11B are diagrams of a micro-light emitting diode (LED)device.

DETAILED DESCRIPTION

We describe here an approach for the massively parallel laser-assistedtransfer of discrete components onto a target substrate. This processcan enable ultra-fast, high throughput, low-cost assembly of largenumbers of discrete components. For instance, light emitting diodes(LEDs) can be rapidly placed onto substrates, thus creating LED arraysfor use in devices such as displays or solid state lighting.

Referring to FIGS. 1A and 1B, a laser-assisted transfer process is usedfor high-throughput, low-cost contactless assembly of discretecomponents onto rigid or flexible substrates. The term discretecomponent refers generally to, for example, any unit that is to becomepart of a product or electronic device, for example, electronic,electromechanical, photovoltaic, photonic, or optoelectronic components,modules, or systems, for example any semiconductor material having acircuit formed on a portion of the semiconducting material. The discretecomponents can be ultra-thin, meaning having a maximum thickness of 50μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less,10 μm or less, or 5 μm or less. The discrete components can beultra-small, meaning having a maximum length or width dimension lessthan or equal to 300 μm per side, 100 μm per side, 50 μm per side, 20 μmper side, or 5 μm per side. The discrete components can be bothultra-thin and ultra-small.

Referring specifically to FIG. 1A, a discrete component 12 is adhered toa carrier substrate 16 by a dynamic release layer 22. The term carriersubstrate refers generally to, for example, any material including oneor more discrete components, for example, a collection of discretecomponents assembled by a manufacturer, such as a wafer including one ormore semiconductor dies.

The discrete component 12 includes an active face 32, which includes anintegrated circuit device. In the example of FIGS. 1A and 1B, the activeface 32 of the discrete component 12 faces away from the dynamic releaselayer 22; in some examples, the active face 32 can face toward thedynamic release layer 22.

Referring also to FIG. 1B, in a blistering transfer process, the energyof the laser beam 24 is applied to a back side 30 of the carriersubstrate 16. The carrier substrate 16 is transparent to the wavelengthof the laser energy. The laser energy 24 thus passes through the carriersubstrate 16 and is incident on an area of the dynamic release layer 22,causing ablation of a partial thickness of the dynamic release layer inthe area on which the laser energy 24 is incident (which we refer to asthe irradiated area). The ablation generates confined gas, which expandsand generates a stress in the non-ablated remainder of the dynamicrelease layer 22. The stress causes the material of the dynamic releaselayer to deform elastically, forming a blister 26. If the stressresulting from the elastic deformation exceeds the yield strength of thedynamic release layer material, the dynamic release layer deformsplastically. The blister 26 exerts a mechanical force on the discretecomponent 12. When the mechanical force exerted by the blister 26 issufficient to overcome the adhesion between the discrete component 12and the dynamic release layer 22, the mechanical force exerted by theblister 26 (in combination with gravity) propels the discrete componentaway from the carrier substrate 16, e.g., for transfer to a targetsubstrate 28.

In an ablative transfer process, the energy of the laser beam 24 isapplied to the back side 30 of the transparent carrier substrate, asshown in FIG. 1B. The laser energy 24 incident on an area of the dynamicrelease layer 22 causes ablation of the complete thickness of thedynamic release layer 22 in the irradiated area, thereby eliminating anyadhesion between the discrete component 12 and the carrier substrate 16.The gases generated by the ablation, in combination with gravity, propelthe discrete component 12 away from the carrier substrate 16, e.g., fortransfer to the target substrate 28.

Further description of a laser-assisted transfer process by blisteringof the dynamic release layer can be found in U.S. Patent Publication No.US2014/0238592, the contents of which are incorporated here by referencein their entirety.

In some examples, a laser-assisted transfer process can be used totransfer multiple discrete components concurrently or near concurrently.We sometime use the term concurrently to mean generally concurrently ornear concurrently. This process, sometimes referred to as massivelyparallel laser-assisted transfer, can enable ultra-fast, high throughputtransfer of discrete components onto a target substrate.

Referring to FIG. 2A, multiple discrete components 112 are adhered to asingle carrier substrate 116 by a dynamic release layer 122. Themultiple discrete components 112 can be arranged in an array, such as aone-dimensional array or a two-dimensional array. The dynamic releaselayer 122 of FIG. 2A can include one or more layers.

Referring also to FIG. 2B, the energy of the laser beam 124 is used forconcurrent laser-assisted transfer of the multiple discrete components112 onto a target substrate 128. The carrier substrate 116 istransparent to the wavelength of the laser beam 124. The laser beam 124is divided into multiple beamlets 140 a, 140 b, 140 c by an opticalelement 142, such as a diffractive optical element, e.g., a beamsplitter. By beamlet, we mean a beam of light, such as a beam of lighthaving a smaller size (e.g., diameter) than the laser beam 124. Each ofthe multiple beamlets 140 a, 140 b, 140 c is incident concurrently witheach of the other beamlets on a corresponding region of the dynamicrelease layer 122 that is aligned with one of the multiple discretecomponents 112. In a blistering transfer, the laser energy of each ofthe multiple beamlets 140 a, 140 b, 140 c induces concurrent formationof a blister 126 at each of the regions of the dynamic release layer122. The concurrent formation of multiple blisters 126 causes all of thediscrete components 112 aligned with the irradiated regions of thedynamic release layer 122 to separate concurrently from the dynamicrelease layer 122, e.g., for transfer to the target substrate 128.

Referring to FIG. 2C, in some examples, an ablative transfer can be usedfor concurrent laser-assisted transfer of the multiple discretecomponents 112 onto the target substrate. In concurrent ablativetransfer, the laser energy of each of the beamlets 140 a, 140 b, 140 cinduces concurrent ablation through the entire thickness of the dynamicrelease layer 122 in the irradiated regions, thereby causing thediscrete components 112 aligned with the irradiated regions to separateconcurrently from the dynamic release layer 122, e.g., for transfer tothe target substrate 128.

In the example of FIG. 2B, the laser beam 124 is divided into threebeamlets to be incident on discrete components 112 arranged in aone-dimensional array. In some examples, the laser beam 124 can bedivided into multiple beamlets to be incident on discrete componentsarranged in a two-dimensional array. The laser beam 124 can be dividedinto a larger number of beamlets, such as 10 beamlets, 100 beamlets, 500beamlets, 1000 beamlets, 5000 beamlets, 10,000 beamlets, or anothernumber of beamlets. The number of beamlets into which the laser beam 124can be divided can be dependent on the energy of the laser producing thelaser beam 124. The number of beamlets can be dependent on the size ofthe discrete components 112 being transferred. For instance, largerdiscrete components can be transferred using a greater amount of energythan smaller discrete components, and thus the laser beam 124 can bedivided into fewer beamlets for transferring larger discrete componentsthan for transferring smaller discrete components.

In some examples, the laser beam 124 is divided into fewer beamlets 140than the number of discrete components 112. The laser beam 124 can bescanned across the carrier substrate 116 to sequentially transfersubsets of the multiple discrete components 112, where the discretecomponents in each subset are transferred concurrently. For instance,the laser beam 124 can be divided into a two-dimensional pattern, e.g.,to transfer a two-dimensional array of discrete components, and thepattern can be scanned across the carrier substrate to releasetwo-dimensional arrays of discrete components concurrently. In someexamples, the pattern can vary for different scan positions, e.g., toaccount for variations in the type, size, or both of the discretecomponents on the carrier substrate.

FIG. 3 shows a perspective view of a discrete component 112 and aportion of a dynamic release layer 322 aligned with the discretecomponent 112. The carrier substrate on which the dynamic release layer322 is adhered is not shown for simplicity. Laser beam 324 is used totransfer the discrete component 112 onto a target substrate. An opticalelement 342 divides the laser beam 324 into a multi-beamlet pattern 326that is incident on the dynamic release layer aligned with the discretecomponent 112. Each beamlet pattern causes either partial-thicknessablation of the dynamic release layer and the formation of blisters, orthrough-thickness ablation of the dynamic release layer, causing a forceto be applied to the discrete component at multiple positions. In thespecific example of FIG. 3, the multi-beamlet pattern 326 includes fourbeamlets 326 a, 326 b, 326 c, 326 d oriented such that the beamlets areincident on the dynamic release layer aligned with the four corners ofthe discrete component 112. This configuration causes a substantiallyequivalent force to be applied to each corner of the discrete component112. The use of a multi-beamlet pattern of laser energy to transfer adiscrete component can help to achieve high yield and precise placementof the discrete component onto the target substrate.

FIG. 4 is a perspective view of multiple discrete components 112 and adynamic release layer 422. The carrier substrate to which the discretecomponents 112 are adhered is not shown for simplicity. Laser beam 424is used for concurrent transfer of the multiple discrete components 112onto a target substrate. The laser beam 424 is divided into amulti-beamlet pattern 426 by a first optical element 428 of an opticalsystem, such as a diffractive optical element, e.g., a beam splitter.The multi-beamlet pattern 426 includes multiple beamlets in anarrangement to be incident on the dynamic release layer aligned with asingle discrete component. For instance, the multi-beamlet pattern 426can include four beamlets of laser energy oriented to be incident on thedynamic release layer aligned with the four corners of a discretecomponent.

The multi-beamlet pattern 426 undergoes a second split at a secondoptical element 430 of the optical system, such as a diffractive opticalelement, e.g., a beam splitter. The second split generates multiplegroups 432 of the multi-beamlet pattern 426 of laser beams. Each group432 is incident on a region of the dynamic release layer that is alignedwith one of the discrete components 112. The multiple beamlets withineach group 432 cause multiple blisters to form in the irradiated regionsof the dynamic release layer, or alternatively, cause through-thicknessablation to form in the irradiated regions of the dynamic release layer.This approach enables concurrent transfer of multiple discretecomponents 112, while the use of multiple beamlets per discretecomponent can help to achieve high yield and precise placement of thediscrete components onto the target substrate.

In the specific example of FIG. 4, the laser beam 424 is divided by thefirst optical element 428 into a pattern 426 including four beamlets,one beamlet for each corner of a discrete component. The pattern 426 isdivided by the second optical element 430 into three groups 432 a, 432b, 432 d, each group including four beamlets of laser energy. Each group432 is incident on a region of the dynamic release layer 422 that isaligned with a corresponding one of the multiple discrete components112, and within each group the four beamlets are incident on the dynamicrelease layer aligned with the four corners of the correspondingdiscrete component 112.

In the example of FIG. 4, the optical system includes two opticalelements 428, 430. In some examples, the optical system can include asingle optical element that divides the laser beam 424 into multiplepatterns, each pattern including multiple beamlets of laser energy.

In some examples, the pattern 426 of laser beamlets is divided intofewer groups 432 than the number of discrete components 112. The set ofgroups 432 can be scanned across the carrier substrate (not shown) tosequentially transfer subsets of the multiple discrete components, wherethe discrete components in each subset are transferred concurrently.

In examples in which the laser beam is scanned across the carriersubstrate, the energy density incident on the dynamic release layer canchange as the laser energy is scanned, e.g., due to variations in thedistance the laser energy travels from its source and the angle at whichthe laser energy strikes the dynamic release layer. Differences inenergy density can affect the positional accuracy with which thediscrete components are transferred onto the target substrate and theyield of the transfer process. In some examples, the energy density(e.g., the laser fluence) can be adjusted to compensate for variationsin the angle at which the layer energy strikes the dynamic release layeror variations in the distance between the source of the laser energy andthe points at which the laser energy strikes the dynamic release layer.In some examples, the energy density can be adjusted in accordance withchanging the pattern of beamlets, e.g., due to a change in a number ofdiscrete components to be transferred concurrently or due to a change ina number of beamlets to be incident on a single discrete component. Insome examples, an optical element such as a lens, e.g., a telecentriclens, can be used to reduce the variation in the angle at which thelaser energy strikes the dynamic release layer, thus reducingdifferences in energy density. In some examples, the output power of thelaser can be adjusted based on the release process, e.g., adjusted byscan position or by the pattern of beamlets or by another aspect of therelease process.

In some examples, the optical system is configured to be switchedbetween single-component mode in which a single discrete component isindividually transferred and a multiple-component mode in which multiplediscrete components are transferred concurrently. In an example, themultiple discrete components 112 on the carrier substrate may bediscrete components from a wafer. Single-component mode can be used totransfer one or more undesired discrete components to a destination,such as a test substrate or a discard. For instance, undesired discretecomponents can be discrete components having circuitry that failed atest. Multiple-component mode can then be used to transfer one or moreof the remaining discrete components to the target substrate.

In some examples, after the multiple-component mode transfer of one ormore of the remaining discrete components to the target substrate,single-component mode can be used again to transfer additional discretecomponents to positions on the target substrate that are missing adiscrete component (e.g., because the discrete component at thatposition had been removed as undesirable, was originally missing from asource substrate, or for another reason). For instance, single-componentmode can be used to transfer discrete components that were nottransferred during the multiple-component transfer, e.g., discretecomponents from the circumferential region of a wafer. The ability totransfer discrete components in single-component mode can help increaseyield, e.g., by enabling transfer of discrete components, such ascomponents near the edge of a wafer, that may be difficult to include ina group of concurrently transferred discrete components.

In some examples, undesired discrete components can be identified basedon a wafer map indicating a characteristic of each of one or more of thediscrete components on the carrier substrate. In some examples, thewafer map can be created based on testing before the discrete componentsare adhered to the carrier substrate. For instance, the wafer map can becreated based on a testing of each discrete component followingmanufacturing of the discrete components, and the undesired discretecomponents can be those components having circuitry that failed thepost-manufacturing test. Testing can include electrical testing of thecircuitry of the discrete component, optical testing of the opticaloutput of an LED discrete component, or other types of testing (e.g.,testing of the functionality of a sensor on the discrete component orthe operation of a microelectromechanical (MEMS) device on the discretecomponent). In some examples, the wafer map can be created based on insitu testing of the discrete components on the carrier substrate. Forinstance, when the discrete components are optoelectronic devices, aphotoluminescence (PL) test can be performed in which each discretecomponent is excited with low power laser energy and the opticalresponse after relaxation to ground state is detected. The opticalresponse can be used to characterize the component.

FIGS. 5A-5C and 6A-6C show examples of this multiple-transfer process,which we sometimes call a “good-die-only” transfer process.

Referring specifically to FIG. 5A, discrete components 550 arranged inan array are adhered to a carrier substrate 552 by a dynamic releaselayer. A mapping indicates a characteristic of each of one or more ofthe discrete components 550 in the array. For instance, the mapping canbe indicative of results of a post-manufacturing test, a quality controltest, or an in situ test, e.g., as described above, and can indicatewhether each discrete component passed or failed the test. Discretecomponents that passed the test (e.g., discrete components that satisfya quality criterion) are sometimes referred to as “good die” anddiscrete components that failed the test (e.g., discrete components thatdo not satisfy the quality criterion) are sometimes referred to as “baddie.” In the example mapping of FIG. 5A, bad die (e.g., the discretecomponent 550 a) are shaded in dark gray and good die (e.g., thediscrete component 550 b) are shaded in light gray. In a first transferstep, the bad die are transferred in single-component mode to adestination, such as a test substrate or a discard.

Referring to FIG. 5B, once the bad die have been transferred in thesingle-component mode transfer, there is an empty position in the arrayon the carrier substrate 552 where each bad die was originally located.For instance, an empty position 554 in the array corresponds to thelocation of the bad die 550 a. At least a portion of the remainingdiscrete components, which are the good die, are transferred to a targetsubstrate 556 in a second, multiple-component transfer step, thusforming a second array of transferred discrete components 550′ on thetarget substrate.

A transfer field 558 can define on the carrier substrate 552 a region ofa desired size, a region encompassing a desired number array positions,or a region encompassing a desired number of discrete components. Themultiple-component transfer process can transfer only some or all ofthose discrete components that are encompassed within the transfer field558. Any discrete components that are outside the transfer field 558 arenot transferred to the target substrate 556, and remain on the carriersubstrate 552 as remaining discrete components 560. In the example ofFIG. 5B, the transfer field 558 is sized to encompass a 10×10 array, andthe multiple-component transfer process transfers all of the discretecomponents encompassed within the transfer field. The array oftransferred discrete components 550′ on the target substrate 556 is thusa 10×10 array of discrete components (and empty positions, if any) inwhich the relative positioning of discrete components and emptypositions is preserved. The transfer field can be sized based on adesired size or number of discrete components for a downstreamapplication, such as a light emitting diode (LED) based display.

Referring to FIG. 5C, in some examples, the empty positions in the arrayof transferred discrete components 550′ on the target substrate arefilled in by a third transfer step. In the third transfer step, each ofone or more of the remaining discrete components 560 (e.g., a remaininggood discrete component) is transferred in a single-component modetransfer process to one of the empty positions (e.g., the empty position554′, see FIG. 5B) on the target substrate 556. In some examples, theempty positions can be filled in by transferring discrete componentsfrom a different carrier substrate, e.g., if there are not enoughdiscrete components remaining on the carrier substrate 552 or if adifferent type of discrete component is desired. At the completion ofthe third transfer process, the array of transferred discrete components550′ on the target substrate 556 is a complete array of good discretecomponents with no empty positions.

Referring to FIGS. 6A-6C, in some examples, a good-die-only transferprocess transfers a specified pattern of discrete components from thecarrier substrate to the target substrate. Referring specifically toFIG. 6A, discrete components 580 arranged in an array are adhered to acarrier substrate 582 by a dynamic release layer. A mapping of acharacteristic of the discrete components 580 indicates bad die (e.g.,the discrete component 580 a) in dark gray and good die (e.g., thediscrete component 580 b) in light gray. In a first transfer step, thebad die are transferred in single-component mode to a destination, suchas a test substrate or a discard.

Referring to FIG. 6B, once the bad die have been transferred in thesingle-component mode transfer, there is an empty position in the arrayon the carrier substrate 582 where each bad die was originally located.A pattern of the remaining discrete components, which are the good die,are transferred to a target substrate 586 in a second,multiple-component transfer step, thus forming a second transferredarray of transferred discrete components 580′ on the target substrate.For instance, a pattern of discrete components encompassed within atransfer field 588 can be transferred. In the example of FIG. 6B, thediscrete components at every other location in the array on the carriersubstrate 582 is transferred; if there is an empty position at one ofthese locations, that empty position remains also in the transferredarray. Referring to FIG. 6C, in some examples, the empty positions inthe array of transferred discrete components 580′ on the targetsubstrate are filled in by a third transfer step, e.g., by transferringremaining discrete components from the carrier substrate 582 or fromanother carrier substrate.

In some examples, the third transfer step is not executed and the emptypositions in the array of transferred discrete components remain whenthe target substrate is provided to downstream application. Forinstance, the third transfer step can be eliminated if the density ofdiscrete components in the array is sufficient that a small number ofempty positions will not substantially affect the performance of thearray in the downstream application. In some examples, the thirdtransfer step is optional and can be carried out based on the array oftransferred discrete components satisfying (or not satisfying) a qualitycharacteristic. For instance, the third transfer step can be executedwhen there are more than a threshold number or percentage of emptypositions, or when a threshold number of empty positions are adjacent toother empty positions.

Referring to FIG. 7, the good-die-only process such as that shown inFIGS. 5A-5C and 6A-6C can be carried out on a transfer apparatus 750that is capable of switching between multiple-component mode andsingle-component mode. For instance, the transfer apparatus 750 caninclude an automated optical element changer 752 that enables variousoptical systems 754 a, 754 b, 754 c to be moved into alignment with alaser 753, e.g., depending on the type of transfer process (e.g.,multiple-component mode or single-component mode). In an example, theoptical system 754 a can be a single-beam system and the optical systems754 b, 754 c can be multi-beam systems with different beamconfigurations. Other configurations of optical systems are alsopossible. In some examples, the transfer apparatus 750 can includemultiple optical elements in the path of the laser beam or beamlets, andthe automated optical element changer 752 can move one of the multipleoptical elements into or out of the path. The transfer apparatus caninclude a scanning mechanism (not shown) that can scan the laser beam orbeamlets output from each optical system across the surface of a carriersubstrate 758 to transfer one or more discrete components 760.

The apparatus can be computer-controlled by one or more local or remotecomputers or controllers 762 such that the end-to-end multiple-transferprocess can be automated. For instance, a controller can control thealignment of the laser beam or beamlets with each discrete component tobe transferred in the first single-component mode transfer. Thecontroller can control the alignment of the laser beam or beamlets withthe discrete components to be transferred in the second multi-componenttransfer. The controller can control the alignment of the laser beam orbeamlets with each of the remaining discrete components to betransferred in the single-component mode third transfer, and can controlthe alignment of the carrier substrate with the target substrate duringthe single-component mode third transfer. The apparatus can include astimulus application device 764 configured to output a stimulus, such asultraviolet light or heat, to be applied to the carrier substrate, e.g.,to reduce the adhesion of the dynamic release layer.

The transfer apparatus can include a target substrate holder 766 forholding the target substrate. In some examples, the target substrateholder 766 can hold multiple target substrates. In some examples, suchas in the example apparatus 750 of FIG. 7, the target substrate holder766 can hold a single target substrate 768′ in position to receivediscrete components transferred from the carrier substrate 758. Atransfer rack 770 configured to hold one or more target substrates 768can be controlled by a controller 772 to move individual targetsubstrates from the transfer rack 770 to the target substrate holder766. As an example, a first target substrate can be held by the targetsubstrate holder 766 to receive a first transfer (e.g., bad die) fromthe carrier substrate 758. A second target substrate can then betransferred from the transfer rack 770 into the target substrate holder766 to receive a second transfer (e.g., good die) from the carriersubstrate 758.

The transfer apparatus can include a carrier substrate holder 774 forholding the carrier substrate 758. In some examples, the carriersubstrate holder 774 can hold multiple carrier substrates. In someexamples, such as in the example apparatus 750 of FIG. 7, the carriersubstrate holder 774 can hold a single carrier substrate. In someexamples, a transfer rack (not shown) configured to hold one or morecarrier substrates can be controlled to move individual substrates fromthe transfer rack to the carrier substrate holder 774.

Referring to FIG. 8, in some examples, single-component mode ormultiple-component mode can be used to sort discrete components 600 heldon a carrier substrate 602 by one or more characteristics of thediscrete components. For instance, when the discrete components areLEDs, the characteristic can be an emission wavelength, quantum output,a turn-on voltage, a light intensity, a voltage-current characteristic,or another characteristic, or a combination of any two or more of them.The characteristic can be indicated in a mapping that indicates thecharacteristic for each of one or more of the discrete components heldon the carrier substrate 602. In the sorting process, each set ofdiscrete components that share a common characteristic or combination ofcharacteristics is transferred to a corresponding target substrate,resulting in a set of target substrates, each target substrate having aset of discrete components that share a common characteristic (e.g., acharacteristic falling into a common range) or combination ofcharacteristics. The discrete components sharing a common characteristicor combination of characteristics can be transferred individually insingle-component mode or concurrently in multiple-component mode.

The transfer apparatus 750 of FIG. 7 can be used for sorting discretecomponents by characteristics of the discrete components. In someexamples, the target substrate holder 766 can hold multiple targetsubstrates, and discrete components from a single carrier substrate 758can be transferred to respective target substrates held in the targetsubstrate holder 766 based on a characteristic of the discretecomponents. In some examples, the target substrate holder 766 can hold asingle target substrate. A first set of discrete components from thecarrier substrate 758 sharing a common characteristic or combination ofcharacteristics can be transferred to a first target substrate held inthe target substrate holder 766. A second target substrate can then betransferred into the target substrate holder 766 and a second set ofdiscrete components with a different common characteristic orcombination of characteristics can be transferred to the second targetsubstrate.

In the example of FIG. 8, discrete components 604 having a firstcharacteristic in common (e.g., LEDs having an emission wavelength in afirst range) are transferred from the carrier substrate 602 to a firsttarget substrate 606 in a first multiple-component mode transfer.Discrete components 608 having a second characteristic in common (e.g.,LEDs having an emission wavelength in a second range) are transferredfrom the carrier substrate 602 to a second target substrate 610 in asecond multiple-component mode transfer. Discrete components 612 havinga third characteristic in common (e.g., LEDs having an emissionwavelength in a third range) are transferred from the carrier substrate602 to a third target substrate 614 in a third multiple-component modetransfer. Although three target substrates are shown in FIG. 8, thesorting process can transfer sets of discrete components to any numberof target substrates.

Referring to FIG. 9, in an example process for transferring discretecomponents, singulated discrete components are provided on a temporarysubstrate, such as a dicing tape; or on a donor substrate such as awafer, e.g., a silicon wafer or a sapphire wafer (700). For instance, awafer can be adhered to the dicing tape and diced into the discretecomponents. Prior to adhering the wafer to the dicing tape, the wafercan be thinned, e.g., to a thickness of about 50 μm. Further descriptionof dicing a wafer into discrete components is provided in PCTApplication Serial No. PCT/US2017/013216, filed Jan. 12, 2017, thecontents of which are incorporated here by reference in their entirety.

The singulated discrete components are transferred from the temporarysubstrate to a transparent carrier substrate having a dynamic releaselayer disposed thereon (702). In some examples, the carrier substratecan be provided with the dynamic release layer already applied. In someexamples, the dynamic release layer is applied to the carrier substrate.The carrier substrate is formed of a material, such as glass or atransparent polymer, that is at least partially transparent to at leastsome wavelengths of the ultraviolet, visible, or infraredelectromagnetic spectrum, including the wavelength(s) to be used duringthe subsequent laser assisted transfer process. In some examples,components of a singulated wafer are transferred directly to the carriersubstrate without the use of a temporary substrate. For instance, directtransfer of singulated components can be used to transfer epi-layerthick micro-LEDs from a growth substrate to a carrier substrate using alaser lift-off process.

In some examples, the singulated discrete components are transferred tothe carrier substrate in a good-die-only transfer process in which “baddie” are first removed from the temporary substrate and the remaining“good die” are then transferred to the carrier substrate.

The discrete components are transferred from the temporary substrate tothe carrier substrate by contacting the discrete components on thetemporary substrate to the dynamic release layer on the carriersubstrate. In some examples, when the temporary substrate is a dicingtape, the dicing tape can be formed of a material that undergoes areduction in adhesion responsive to a stimulus, such as heat orultraviolet light. When the dicing tape is exposed to the stimulus, theadhesion of the dicing tape is reduced, thereby facilitating thetransfer of the discrete components to the carrier substrate. Furtherdescription of transferring discrete components onto a carrier substrateis provided in PCT Application Serial No. PCT/US2017/013216, filed Jan.12, 2017, the contents of which are incorporated here by reference intheir entirety.

In some examples, the discrete components can be transferred to thecarrier substrate before dicing, e.g., as a whole or partial wafer. Forinstance, the wafer or partial wafer can be mounted on the carriersubstrate and then the wafer can be diced into the discrete components.In some examples, the wafer can be partially diced prior to the transferto the carrier substrate and the dicing can be completed after thetransfer to the carrier substrate.

In some examples, the dynamic release layer can be a material withcontrollable adhesion, such as a material with an adhesion that can bereduced upon exposure to a stimulus, such as heat, ultraviolet light, oranother stimulus. When the discrete components are transferred to thecarrier substrate, a highly adhesive dynamic release layer facilitatesthe transfer and helps to secure the discrete components on the carriersubstrate. However, a less adhesive dynamic release layer can facilitatea subsequent laser-assisted transfer of the discrete components to atarget substrate. Accordingly, in some examples, once the discretecomponents have been transferred to the carrier substrate, the adhesionof the dynamic release layer is reduced (704), e.g., by exposing thedynamic release layer to a stimulus such as heat or ultraviolet light.Adhesion reduction causes reduced adhesion for the entire dynamicrelease layer, and facilitates subsequent laser-assisted transfer.Adhesion reduction is optional, as indicated by the dashed line borderin FIG. 8. For instance, in an ablative laser-assisted transfer process,adhesion reduction is not generally performed. Further description ofdynamic release layers having controllable adhesion is provided in PCTApplication Serial No. PCT/US2017/013216, filed Jan. 12, 2017, thecontents of which are incorporated here by reference in their entirety.

In some examples, in a sorting process, the discrete components aretransferred from the carrier substrate to multiple target substrates inmultiple laser-assisted transfer processes (706). For instance, thediscrete components can be transferred to target substrates based on acharacteristic of the discrete components, thereby sorting the discretecomponents by that characteristic. The outcome of the sorting process isa set of target substrates, each target substrate having a set ofdiscrete components that share a common characteristic.

In some examples, each target substrate can have die catching materialdisposed thereon. The die catching material (DCM) can be a material thatreceives discrete components as they are transferred from the carriersubstrate and keeps them in their targeted positions while reducingpost-transfer movement of the discrete components on the targetsubstrate. The DCM can be selected based on properties such as surfacetension, viscosity, and rheology. For instance, the DCM can provideviscous drag to prevent discrete component movement, or can preventdiscrete component movement by another externally-applied force, such asan electrostatic force, a magnetic force, a mechanical force, or acombination of any two or more of them.

In some examples, the target substrates are provided with the diecatching material already applied. In some examples, the DCM is appliedto the target substrates prior to transfer of the discrete components.DCM can be applied as a continuous film, e.g., with a thickness ofbetween about 3 μm and about 20 μm, using a film deposition method suchas spin coating, dip coating, wire coating, doctor blade, or anotherfilm deposition method. Alternatively, DCM can be applied as a discrete,patterned film, e.g., in the locations at which discrete components areto be placed. A patterned DCM film can be formed by material printingtechniques such as stencil printing, screen printing, jetting, inkjetprinting, or other techniques. A patterned DCM film can also be formedby pre-treating the target substrate with a pattern of a material thatattracts the DCM, a material that repels the DCM, or both, and thenusing a continuous film deposition method to deposit the DCM, resultingin DCM in the regions with the DCM-attracting material (or in theregions without the DCM repelling material). For instance, the targetsubstrate can be patterned with hydrophilic material, hydrophobicmaterial, or both.

In some examples, the discrete components on each target substrate aretransferred to a corresponding second substrate, such as a tape (708).Because the discrete components were sorted by characteristic during thetransfer to the target substrate, each tape will thus also receivediscrete components sharing a common characteristic. The tapes can beprovided for downstream applications, e.g., to end productmanufacturers. The transfer of the discrete components to the secondsubstrate can be a contact transfer. When the target substrates includea layer of die catching material with controllable adhesion, theattachment element can be exposed to a stimulus to reduce the adhesion,thereby facilitating transfer of the discrete components.

In some examples, the discrete components are transferred to a devicesubstrate in a laser-assisted transfer process (710). The transfer ofthe discrete components to the device substrate can include agood-die-only transfer process as described above, in which bad die arefirst transferred from the carrier substrate to a discard, and an arrayof good die is then transferred concurrently from the carrier substrateto the device substrate.

In some examples, the device substrate can have a conductive attachmentelement disposed thereon to enable die catching and interconnection. Theattachment element cures responsive to an applied stimulus, such as amaterial that is thermally curable, curable upon exposure to ultravioletlight, or curable in response to another type of stimulus, or acombination of any two or more of them. In some examples, the devicesubstrate is provided with the attachment element already applied. Insome examples, the attachment element is applied to the targetsubstrates prior to transfer of the discrete components. In someexamples, the device substrate can have an attachment element disposedthereon that serves as a flux during soldering, and the die catchingmaterial is activated by heating to facilitate soldering as a processfor interconnection of the discrete components. Further description ofattachment elements is provided in PCT Application Serial No.PCT/US2017/013216, filed Jan. 12, 2017, the contents of which areincorporated here by reference in their entirety.

The discrete components are bonded to the device substrate (712). Forinstance, the attachment element can be cured, e.g., by exposure to astimulus such as a high temperature, ultraviolet light, or anotherstimulus, or a combination of any two or more of them, therebyincreasing the adhesion of the attachment element. The stimulus can beremoved after a time sufficient to allow the attachment element to cure,thus forming a mechanical bond, an electrical bond, or both, between thedevice substrate and the discrete components. Further description ofbonding discrete components to a device substrate is provided in PCTApplication Serial No. PCT/US2017/013216, filed Jan. 12, 2017, thecontents of which are incorporated here by reference in their entirety.

The discrete components are interconnected to the device substrate (714)to establish electrical connections between circuit elements on thediscrete components and circuit elements on the device substrate. Insome examples, the discrete components are interconnected to the devicesubstrate in a face-up orientation with the active face of the discretecomponent facing away from the device substrate. The active face of adiscrete component is the surface on which the circuitry of the discretecomponent is formed. For face-up discrete components, interconnectioncan include wire bonding, isoplanar printing (in which a conductivematerial is printed onto the device substrate and the active face of thediscrete component), direct write material deposition, thin filmlithography, or other interconnection methods. In some examples, thediscrete components are interconnected to the device substrate in aface-down orientation (sometimes referred to as “flip-chip”) with theactive face of the discrete component facing toward the devicesubstrate. Flip-chip interconnection can include adhesive bonding,soldering, thermocompression bonding, ultrasonic bonding, or otherflip-chip interconnection methods.

Referring to FIG. 10, in an example process 800 for transferringdiscrete components, such as micro LEDs, singulated discrete componentsare provided on a substrate (802), such as a wafer, e.g., a sapphirewafer.

In some examples, the discrete components are transferred to anintermediate substrate (804), e.g., by contacting the discretecomponents on the donor substrate to the intermediate substrate. Forinstance, an intermediate substrate can be used for cases in which thediscrete component is to be flipped (i.e., turned over 180°) for anultimate downstream application. An intermediate substrate can alsosometimes improve a metric associated with the transfer process, such asyield, accuracy, or another metric. The discrete components are thentransferred from the intermediate substrate to a transparent carriersubstrate having a dynamic release layer disposed thereon (806).

In some examples, the intermediate substrate is not used and thediscrete components are transferred directly from the donor substrate tothe transparent carrier substrate. In such cases, the aspect 804 of thetransfer process is skipped and the aspect 806 of the transfer processis a transfer of the discrete components from the donor substratedirectly to the transparent carrier substrate. The transfer of thediscrete components from the substrate (e.g., the sapphire wafer) toeither the intermediate substrate or the carrier substrate can beperformed by a laser liftoff process. In a laser liftoff process, theactive (functional) layers of a component are separated from a substrateby changing the material composition at an interfacial layer between thefunctional layers and the substrate. For instance, in a laser liftoffprocess of GaN micro-LEDs grown epitaxially on a sapphire substrate, alaser (e.g., an ultraviolet laser) is focused on the interface betweenthe GaN layers of the micro-LEDs and the sapphire substrate. The hightemperature in the area on which the laser is focused causesdecomposition of a thin (e.g., less than 1 μm thick) layer of GaN intogallium and nitrogen. The melting point of gallium is very low (about30° C.), thus enabling the functional GaN layers of the micro-LEDs to beeasily removed by melting the gallium layer.

The adhesion of the dynamic release layer is reduced (808) byapplication of a stimulus, such as heat, ultraviolet light, or anothertype of stimulus. The discrete components are then transferred using alaser-assisted transfer process to a device substrate (810). In theexample of FIG. 10, the discrete components are shown as beingtransferred individually in single-component mode. In some examples,multiple discrete components can be transferred concurrently inmultiple-component mode. In some examples, the discrete componenttransfer includes the good-die-only process in which bad die are removedfrom the carrier substrate in a first transfer process and good die arethen transferred to the device substrate in a second transfer process.The discrete components on the device substrate are bonded to the devicesubstrate and interconnected to circuit elements on the device substrate(812).

The approaches described above for massively parallel laser-assistedtransfer of multiple discrete components can be used to assemblemicro-LEDs for use in micro-LED-based devices, such as displays, e.g.,television screens or computer monitors; or solid state lighting.Micro-LED-based devices include an array of micro-LEDs, each micro-LEDforming an individual pixel or sub-pixel element. In some examples,colors can be achieved by using micro-LEDs that emit differentwavelengths. In some examples, colors can be achieved by usingmicro-LEDs in conjunction with spectrum shifting materials such asorganic dyes, phosphors, quantum dots, or by using color filters.

By micro-LEDs, we mean LEDs having at least one lateral dimension of atmost 100 microns. By spectrum-shifting material, we mean a material thatis excited by light at a first wavelength (sometimes referred to as anexcitation wavelength) to emit light at a second wavelength (sometimesreferred to as an emission wavelength) different from the excitationwavelength. When a spectrum shifting material is implemented by colorfilters, the color of the spectrum shifting material is the color thatcorresponds to the wavelength of light emitted by the spectrum shiftingmaterial. When a spectrum shifting material is implemented by quantumdots, the color of the spectrum shifting material depends on the size ofthe quantum dots. When a spectrum shifting material is implemented byorganic dyes or phosphors, the color of the spectrum shifting materialdepends on the composition of the dye or phosphor.

Referring to FIGS. 11A and 11B, a micro-LED device 500 includes asubstrate 502 with an array of pockets 504 formed in a top surface ofthe substrate 502. Each pocket 504 corresponds to a sub-pixel of thedevice 500. The pockets 504 can be formed by embossing, lithography, oranother manufacturing method. Spectrum shifting material 506 is disposedin at least some of the pockets 504. The color of the spectrum shiftingmaterial 506 can vary across the array of pockets 504, e.g., by row, bycolumn, in another pattern, or randomly. In the example of FIGS. 11A and11B, the color of the spectrum shifting material 506 varies by column ofthe array of pockets 504, such that a first column 508 a has redspectrum shifting material in its pockets 504, a second column 508 b hasgreen spectrum shifting material in its pockets 504, and a third column508 c has blue spectrum shifting material in its pockets. The substrate502 can be made of a material that is transparent to the colors of thespectrum shifting material. For instance, the substrate 502 can be glassor a transparent polymer.

A micro-LED 510 is placed into each pocket 504 in the substrate 502. Forinstance, the micro-LEDs 510 can be placed into the pockets 504 usingthe approaches described above for massively parallel laser-assistedtransfer of multiple discrete components. The micro-LEDs 510 are placedin the pockets 504 with the spectrum shifting material 506 encompassingthe light-emitting surfaces and side surfaces of the micro-LEDs 510. Themicro-LEDs 510 emit light of a wavelength that can excite the spectrumshifting material 506 to emit light. For instance, the micro-LEDs canemit ultraviolet light.

In the example of FIGS. 11A and 11B, the micro-LEDs 510 are controlledby a passive matrix in which electrical contacts 512 on the oppositeside of the micro-LEDs 510 are exposed toward a top surface 514 of thesubstrate 502. Row and column electrodes 516, 518 are connected to theelectrical contacts 512 of the micro-LEDs 510, providing a way toaddress each micro-LED 510 individually to excite a given pixel orsub-pixel of spectrum shifting material 506. A planarization layer 520is formed over the top surface 514. The planarization layer 520 can betransparent or opaque to light from the spectrum shifting material 506.In some examples, the micro-LEDs are controlled by active matrixtechnology in which each micro-LED is controlled individually usingelectronic components such as thin film transistors and capacitors.

The transparent substrate is transparent to the light emitted by thespectrum shifting materials but absorbs the light emitted by themicro-LEDs. The planarization layer can be transparent or opaque to thelight emitted by the spectrum shifting material.

In some examples, the walls of the substrate 502 between the pockets 504absorb the light emitted by the micro-LEDs 510, preventing the lightfrom one micro-LED from exciting the spectrum shifting material 506 in adifferent pocket 504 and thus reducing or eliminating cross-talk andcolor pollution between neighboring sub-pixels. The presence of thespectrum shifting material 506 encompassing the light-emitting surfacesand side surfaces of the micro-LEDs 510 can also help to reduce oreliminate cross-talk and color pollution. In some examples, the walls ofthe substrate 502 between the pockets 504 can be metallized to reduce oreliminate cross-talk, to improve quantum efficiency by reflecting lightthat may otherwise have been lost to absorption by the walls, and toimprove the directionality of the emitted light.

The micro-LEDs 510 can be assembled into the device 500 using theapproaches described above for massively parallel laser-assistedtransfer of multiple discrete components. Using these approaches, themicro-LEDs 510 can be assembled quickly, enabling high throughputfabrication. For instance, assembling micro-LEDs into a full HD displayusing the approaches described above would take less than about tenminutes, such as about 1 minute, about 2 minutes, about 4 minutes, about6 minutes, about 8 minutes, or about 10 minutes. In contrast,transferring each micro-LED individually to assemble the same displayusing contemporary conventional approaches would take one or more hoursof magnitude longer, such as about 100 hours, about 200 hours, about 400hours, about 600 hours, or about 800 hours.

In some examples, the approaches described here for concurrent transferof multiple discrete components can be used for assembly of otherdevices, such as micro solar cells or microelectromechanical (MEMS)devices. For instance, to assemble components of MEMS mirrors, thepattern of the beamlets of laser energy can be dynamically changedaccording to the specifications of the mirror. Another example is theheterogeneous integration of system-on-chip (SoC) or system-in-package(SiP) components, where a large number of functional blocks (chiplets)need to be transferred to an interposer substrate where they areaggregated together to form the SoC/SiP component.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, some of the steps described above may be order independent, andthus can be performed in an order different from that described.

Other implementations are also within the scope of the following claims.

What is claimed is:
 1. A method comprising: transferring multiplediscrete components from a substrate, the discrete components beingadhered to the substrate by a dynamic release layer, the transferringincluding: individually transferring each of one or more first discretecomponents from the substrate to a first destination using a firstlaser-assisted transfer process, the first discrete components notsatisfying a quality criterion; and transferring multiple seconddiscrete components from the substrate to a second destination using asecond laser-assisted transfer process, the second discrete componentssatisfying the quality criterion.
 2. The method of claim 1, in whichtransferring the multiple second discrete components comprisestransferring fewer than all of the second discrete components such thatone or more second discrete components remain adhered to the substrate.3. The method of claim 2, comprising individually transferring each ofone or more of the second discrete components that remain adhered to thesubstrate to the second destination.
 4. The method of claim 3, in whichthe multiple second discrete components form an array of discretecomponents at the second destination, and in which individuallytransferring each of one or more of the second discrete components thatremain comprises transferring each remaining second discrete componentto an empty position in the array.
 5. The method of claim 1, in whichthe second laser-assisted transfer process comprises: irradiatingmultiple regions on a top surface of the dynamic release layer, each ofthe irradiated regions being aligned with a corresponding one of thesecond discrete components, in which the irradiation causes the seconddiscrete components to be concurrently released from the substrate. 6.The method of claim 1, in which the first laser-assisted transferprocess comprises, for each of the first discrete components:irradiating a region on a top surface of the dynamic release layer, theregion being aligned with the first discrete component, in which theirradiation causes the first discrete component to be released from thesubstrate.
 7. The method of claim 1, comprising reducing an adhesion ofthe dynamic release layer prior to transferring the one or more firstdiscrete components.
 8. The method of claim 7, in which reducing theadhesion of the dynamic release layer comprises exposing the dynamicrelease layer to one or more of heat and ultraviolet light.
 9. Themethod of claim 1, in which the second destination comprises a targetsubstrate, and in which transferring the multiple second discretecomponents to the second destination comprises transferring the multiplesecond discrete components onto attachment elements disposed on a topsurface of the target substrate.
 10. The method of claim 9, comprisingcuring the attachment elements to bond the multiple second discretecomponents to the target substrate.
 11. The method of claim 10, in whichcuring the attachment elements comprises exposing the attachmentelements to one or more of heat, ultraviolet light, and mechanicalpressure.
 12. The method of claim 9, comprising applying the attachmentelements to the target substrate.
 13. The method of claim 1, in whichthe second destination comprises a target substrate, and comprisingbonding the transferred second discrete components to the targetsubstrate.
 14. The method of claim 1, in which the second destinationcomprises a target substrate having circuit components, and in which themethod comprises interconnecting circuit components of the transferredsecond discrete components to the circuit components of the targetsubstrate.
 15. The method of claim 1, comprising transferring thediscrete components from a donor substrate to the substrate.
 16. Themethod of claim 15, in which transferring the discrete components fromthe donor substrate to the substrate comprises contacting the dynamicrelease layer on the substrate to the discrete components on the donorsubstrate.
 17. The method of claim 15, comprising singulating thediscrete components on the donor substrate.
 18. The method of claim 15,in which the donor substrate comprises a dicing tape.
 19. The method ofclaim 15, in which the donor substrate comprises a wafer.
 20. The methodof claim 1, comprising applying the dynamic release layer to thesubstrate.
 21. A method comprising: transferring discrete componentsfrom a carrier substrate to each of multiple target substrates, thediscrete components being adhered to the carrier substrate by a dynamicrelease layer, the transferring including: transferring a first set ofthe discrete components to a first target substrate using alaser-assisted transfer process, the discrete components in the firstset sharing a first characteristic; and using the laser-assistedtransfer process, transferring a second set of the discrete componentsto a second target substrate, the discrete components in the second setsharing a second characteristic different from the first characteristic.22. The method of claim 21, comprising transferring the discretecomponents from multiple carrier substrates to the multiple targetsubstrates.
 23. The method of claim 22, comprising transferring thediscrete components consecutively from each of the multiple carriersubstrates.
 24. The method of claim 22, in which the transferringcomprises: transferring discrete components from a first carriersubstrate to one or more of the target substrates in a transfer system;removing the first carrier substrate from a transfer position in thetransfer system; placing a second carrier substrate in the transferposition; and transferring discrete components from the second carriersubstrate to one or more of the target substrates.
 25. The method ofclaim 21, in which the transferring comprises: transferring the firstset of the discrete components to the first target substrate in atransfer system; removing the first target substrate from a transferposition in the transfer system; and placing the second target substratein the transfer position for transfer of the second set of the discretecomponents.
 26. The method of claim 21, in which the discrete componentscomprise LEDs, and in which the first and second characteristicscomprise one or more of an optical characteristic and an electricalcharacteristic.
 27. The method of claim 21, in which transferring thefirst and second sets of discrete components to the first and secondtarget substrates comprises transferring each of the discrete componentsin the first and second sets individually to the first and second targetsubstrates.
 28. The method of claim 21, in which transferring the firstand second sets of discrete components to the first and second targetsubstrates comprises at least one of concurrently transferring some orall of the discrete components in the first set to the first targetsubstrate, or concurrently transferring some or all of the discretecomponents in the second set to the second target substrate.
 29. Themethod of claim 21, in which transferring a set of discrete componentsto the corresponding target substrate comprises transferring thediscrete components in the set onto a layer of die catching materialdisposed on a top surface of the target substrate.
 30. The method ofclaim 29, comprising applying the die catching material to each targetsubstrate.
 31. The method of claim 21, comprising reducing an adhesionof the dynamic release layer.
 32. The method of claim 31, in whichreducing the adhesion of the dynamic release layer comprises exposingthe dynamic release layer to one or more of heat and ultraviolet light.33. The method of claim 21, comprising transferring the discretecomponents from a donor substrate to the carrier substrate.
 34. Themethod of claim 33, in which transferring the discrete components fromthe donor substrate to the carrier substrate comprises contacting thedynamic release layer on the carrier substrate to the discretecomponents on the donor substrate.
 35. The method of claim 33, in whichthe donor substrate comprises a dicing tape.
 36. The method of claim 33,in which the donor substrate comprises a wafer.
 37. The method of claim21, comprising applying the dynamic release layer to the carriersubstrate.